Industrial electrical transformer coils are provided with large windings of a conductive sheet metal. The transformer coils may be constructed of a single wound sheet, or may be constructed of multiple windings. The windings may also form multiple cylinders, which nest inside one another, with the cylinder of windings having the smallest diameter forming the interior of the transformer coil and the cylinder of windings having the largest diameter forming the exterior of the transformer coil. Although large transformer coils can weigh five tons or more, the windings are relatively delicate and subject to damage if the transformer coils are lifted or moved improperly.
It is known in the prior art to provide large, dedicated lifting systems to secure and transport transformer coils. Such systems are useful for dismantling transformers when they have failed to determine the root cause of a transformer failure. To properly diagnose a failure, prior art systems are designed to dismantle the failed transformers with minimal distortion of the transformers” inner coils. While such systems are useful in a closed environment, such as a transformer coil manufacturing facility, such systems are not portable. These lifting systems are also too large and expensive to be used on an installation site.
While it is possible to place a transformer coil on a platform and use prior art technology to lift the platform with the transformer coil provided thereon, such a platform would limit underneath access to the interior of the coil. It would be desirable to provide a system for lifting the transformer coil which left the axial center of the transformer coil exposed, to allow the transformer coil to be positioned over a core leg. While it would be possible to provide an opening in the platform on which the transformer coil is placed, once the transformer coil is positioned over the core leg, it would be difficult to remove the platform from the core leg with the transformer coil in position over the platform.
It is also known in the art to employ screw clamps, such as those described in U.S. Pat. No. 4,404,740 to lift a transformer coil. In this type of system, screw clamps having top and bottom clamps are secured to a transformer coil. Threaded bolts running the length of the screw clamps are used to tighten the screw clamps, drawing the bottoms of the screw clamps toward the tops of the screw clamps, and securing the transformer coil therebetween. A plurality of such screw clamps may be secured to the transformer coil. Chains are thereafter secured to the screw clamps and a crane or other lifting device lifts the chains.
While such systems are useful for the lifting of the transformer coil or maintaining the axial core of the transformer coil exposed so that it may be placed over a core leg, such systems have several drawbacks. One drawback associated with such prior art systems is the difficulty involved with installing the screw clamps. To install the screw clamps, the transformer coil must be lifted a substantial distance to accommodate the bottom of the screw clamps. Additionally, after the screw clamps are provided under and over the transformer coil, the threaded bolts of the screw clamps must be individually tightened to prevent the screw clamps from being dislodged.
Another disadvantage of such systems is that the screw clamps are allowed to move independently of one another, thereby exposing the transformer coil to damage if one of the screw clamps were to fail and the remaining screw clamps not being connected or sufficiently coordinated to accommodate the additional weight the failed screw clamp is no longer able to support. Additionally, once the transformer coil is provided over the core leg, the difficulties associated with attaching the screw clamps exists in reverse, with the transformer coil having to be lifted a substantial distance to remove the screw clamps and the individual threaded rods of the screw clamps having to be individually adjusted to allow the screw clamps to be removed from the transformer coil. The size and complexity of the screw clamps also increases the maintenance and potential failure rate of the entire system.
In material handling situations such as lifting and moving a transformer coil, it would be desirable to provide a lightweight and efficient system for securing a transformer coil, lifting the transformer coil, moving the transformer coil and removing the lifting system once the transformer coil has been positioned as desired. It would also be desirable to provide a lifting system that secured the transformer coil in a manner that adjusted the load in the event of the failure of one portion of the lifting system. It would also be desirable to provide a lifting system that was adjustable to lift a single transformer coil cylinder or multiple transformer coil cylinders without having to completely remove the material handling system from the transformer coil. Furthermore, it would be desirable to provide a material handling system for lifting and moving transformer coils that is of a low-cost, lightweight and low maintenance design.
The difficulties encountered in the prior art discussed hereinabove are substantially eliminated by the present invention.